There are several standard busses in use in computer telephony circuits. Among them are the Industry Standard Architecture or ISA bus commonly used as an expansion bus in personal computers, the Signal Computing System Architecture or SCSA bus and the Multi-Vendor Integration Protocol or MVIP voice bus and switching protocol for transmitting signals, voice and video from one PC expansion card to another.
Connections between an expansion card and a bus are generally made by edge connectors located on the cards so that the connection of the card to a corresponding receptacle on the bus establishes both power connections to the electrical components on the card and general purpose signal connections (e.g. for data and addresses).
It has generally been necessary to deactivate or remove power from such a bus during the installation of a card. The physical insertion of the card into the bus generated noise on the bus which often proved deleterious to other cards resident on the bus. For example, data being transmitted along the bus to and from the microprocessor and other cards could be lost during insertion of the new card.
For achieving hot pluggability, it is generally required that the power and signal connections are made in a certain order, i.e., generally the power connections are established before the signal connections. For this reason, cards being installed were susceptible of damage from the application of power to the various portions thereof in an order incompatible with the circuit of the card. Further, the boards already operational on the bus or the card may be damaged as a result of temporary electrical disturbances created by the act of connecting the card to the bus. Such disturbances may also create problems on the bus as the result of electromagnetic interference and regulated voltage levels on the bus may fall out of specification severely affecting other cards connected to the bus.
The connection of a card to a bus without deactivating the bus is generally referred to as "hot pluggable", i.e., the card may be "plugged" into the bus while the bus remains "hot" or active.
Many of the above problems also exist upon the physical removal of an card containing active elements from the bus.
Hot pluggable connections between cards and a motherboard have been developed in which it is not necessary to deactivate the bus during insertion of a new card. One such method is disclosed and claimed in the Weir U.S. Pat. No. 5,473,499 assigned to the assignee of the present invention. As disclosed in the Weir patent, an adaptor or interface circuit is physically connected to the bus and cards are thereafter plugged into the adaptor card, with the adaptor card containing circuitry which sequentially connected ground buses on the card before the power busses, with the application of power to the power busses being initially limited.
In contrast to the use of an adaptor card connected to the bus of a personal computer into which standard protocol and architecture cards may thereafter be plugged, the present invention relates to an adaptor card into which one of the standard cards may be plugged, with the adaptor and card combination thereafter plugged into the computer bus.
Accordingly, it is an object of the present invention to provide a novel adaptor and method by which telephony standard cards such as ISA-, SCSA-, and MVIP- busses may be made hot pluggable.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to. which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.